Method of improving uniformity of metal-to-poly capacitors composed by polysilicon oxide and avoiding device damage

• US 5,658,821 A
• Filed: 09/27/1996
• Issued: 08/19/1997
• Est. Priority Date: 09/27/1996
• Status: Expired due to Term

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Ku, Sue-Mei, Wei, Chih-Shih, Chen, Pei-Hung, Chen, Hsin-Pai
• Primary Examiner(s): Nguyen, Tuan H.
• Application Number:
  US08/721,668
• Time in Patent Office: 326 Days
• Field of Search: 437/60, 437/47, 437/919, 437/52, 148/DIG. 14
• US Class Current: 438/396
• CPC Class Codes: H01L 21/32105 Oxidation of silicon-containing layers
• CPC Class Codes: H01L 28/40 Capacitors

Abstract

A method of forming capacitors comprising polysilicon, polysilicon oxide, metal is described which significantly improves uniformity of capacitance across the silicon integrated circuit wafer and avoids damage to electrical contact regions. A first layer of polysilicon oxide is formed on a polysilicon first capacitor plate. The wafer is then dipped in a buffered oxide etch or subjected to a dry anisotropic etch. The etching conditions the polysilicon layer so that subsequent polysilicon oxide growth is very uniform and controllable. A second polysilicon oxide layer is then formed on the polysilicon first capacitor plate. A layer of silicon nitride is formed on the polysilicon oxide and a second capacitor plate is formed on the layer of silicon nitride completing the capacitor. Improved capacitance uniformity across the wafer is achieved and device damage is avoided.

Claims

1. A method of forming capacitors, comprising the steps of:

providing a silicon substrate having devices formed therein;

providing electrical contact regions on said silicon substrate;

providing field oxide isolation regions in said silicon substrate;

forming a number of polysilicon first capacitor plates on said field oxide isolation regions;

forming a layer of insulator dielectric over said silicon wafer covering said polysilicon first capacitor plates;

removing that part of said layer of insulator dielectric directly over said polysilicon first capacitor plates;

removing that part of said layer of insulator dielectric directly over said electrical contact regions;

forming a first layer of polysilicon oxide over said polysilicon first capacitor plates;

forming a first layer of silicon oxide over said electrical contact regions;

removing said first layer of polysilicon oxide and said first layer of silicon oxide by means of etching;

forming a second layer of polysilicon oxide over said polysilicon first capacitor plates after removing said first layer of polysilicon oxide;

forming a second layer of silicon oxide over said electrical contact regions after removing said first layer of silicon oxide;

forming a layer of silicon nitride over said silicon wafer covering said second layer of polysilicon oxide;

forming a patterned layer of photoresist over said layer of silicon nitride wherein photoresist remains only directly above said polysilicon first capacitor plates;

removing that part of said layer of silicon nitride not directly above said polysilicon first capacitor plates;

forming a layer of first metal over said silicon substrate covering said part of said layer of silicon nitride not directly above said polysilicon first capacitor plate; and

patterning said layer of first metal whereby there is first metal directly above said first capacitor plates, thereby forming second capacitor plates, and first metal directly above said electrical contact regions.

2. The method of claim 1 wherein said polysilicon first capacitor plates have a thickness of between about 150 and 250 Angstroms.

3. The method of claim 1 wherein said first layer of polysilicon oxide has a thickness of between about 150 and 250 Angstroms.

4. The method of claim 1 wherein said second layer of polysilicon oxide has a thickness of between about 150 and 250 Angstroms.

5. The method of claim 1 wherein said removing said first layer of polysilicon oxide and said first layer of silicon oxide uses etching in a wet buffered oxide etch at a temperature of between about 22.5°

and 25°

C. for between about 30 and 40 seconds.

6. The method of claim 1 wherein said removing said first layer of polysilicon oxide and said first layer of silicon oxide uses dry vertical anisotropic etching.

7. The method of claim 1 wherein said layer of silicon nitride has a thickness of between about 280 and 320 Angstroms.

8. The method of claim 1 wherein said electrical contact regions are above source/drain regions of a metal oxide semiconductor field effect transistor.

9. The method of claim 1 wherein said layer of insulator dielectric is borophosphosilicate glass.

10. The method of claim 1 wherein said first layer of polysilicon oxide is thermally grown SiO₂.

11. The method of claim 1 wherein said second layer of polysilicon oxide is thermally grown SiO₂.

12. A method of forming capacitors, comprising the steps of:

providing a silicon substrate having devices formed therein;

providing electrical contact regions on said silicon substrate;

forming a number of polysilicon first capacitor plates on said silicon substrate wherein said polysilicon first capacitor plates are insulated from said silicon substrate by a first dielectric;

forming a layer of second dielectric over said silicon wafer covering said polysilicon first capacitor plates;

removing that part of said layer of second dielectric directly over said polysilicon first capacitor plates;

removing that part of said layer of second dielectric directly over said electrical contact regions;

forming a first layer of polysilicon oxide over said polysilicon first capacitor plates;

forming a first layer of silicon oxide over said electrical contact regions;

removing said first layer of polysilicon oxide and said first layer of silicon oxide by means of etching;

forming a second layer of polysilicon oxide over said polysilicon first capacitor plates after removing said first layer of polysilicon oxide;

forming a second layer of silicon oxide over said electrical contact regions after removing said first layer of silicon oxide;

forming a layer of silicon nitride over said silicon wafer covering said second layer of polysilicon oxide;

forming a patterned layer of photoresist over said layer of silicon nitride wherein photoresist remains only directly above said polysilicon first capacitor plates;

removing that part of said layer of silicon nitride not directly above said polysilicon first capacitor plates;

forming a layer of first metal over said silicon substrate covering said part of said layer of silicon nitride not directly above said polysilicon first capacitor plate; and

patterning said layer of first metal whereby there is first metal directly above said first capacitor plates, thereby forming second capacitor plates, and first metal directly above said electrical contact regions.

13. The method of claim 12 wherein said polysilicon first capacitor plates have a thickness of between about 4000 and 4400 Angstroms.

14. The method of claim 12 wherein said first layer of polysilicon oxide has a thickness of between about 150 and 250 Angstroms.

15. The method of claim 12 wherein said second layer of polysilicon oxide has a thickness of between about 150 and 250 Angstroms.

16. The method of claim 12 wherein said removing said first layer of polysilicon oxide and said first layer of silicon oxide uses etching in a wet buffered oxide etch at a temperature of between about 22.5°

and 25°

C. for between about 30 and 40 seconds.

17. The method of claim 12 wherein said removing said first layer of polysilicon oxide and said first layer of silicon oxide uses dry vertical anisotropic etching.

18. The method of claim 12 wherein said layer of silicon nitride has a thickness of between about 280 and 320 Angstroms.

19. The method of claim 12 wherein said electrical contact regions are above source/drain regions of a metal oxide semiconductor field effect transistor.

20. The method of claim 12 wherein said layer of second dielectric is borophosphosilicate glass.

21. The method of claim 12 wherein said first layer of polysilicon oxide is thermally grown SiO₂.

22. The method of claim 12 wherein said second layer of polysilicon oxide is thermally grown SiO₂.